It is not uncommon to see the amount of data associated with a business venture grow at an exponential pace. To manage the increasing amount of data more efficiently, a database is often created. As the size of the database grows, so do the resources and time involved in processing the data.
In the Virtual Storage System (VSS) environment, storage locations may be categorized into grades that are based on response time. The locations with the lowest response times are faster to respond than locations with a higher response time. The VSS may also operate to categorize data access into access frequency grades. Data with the highest access frequency is considered high temperature data, and data with the lowest access frequency is considered low temperature data. The allocation function of the VSS places data into the graded storage locations according to its access frequency, as specified during the initial allocation request. That is, higher temperature data is placed in faster locations, and lower temperature data is placed in slower locations. After initial allocation, unused storage locations may still exist.
During storage system operation, the VSS may be used to track the access frequency of allocated data, perhaps monitoring its average access frequency. To achieve improved performance, the VSS uses unallocated locations with a faster response time for new data placement, sometimes replacing allocated data based on the recorded access frequency. This process of replacing data is termed “migration”. This process can work well in systems with steady-state allocation/de-allocation patterns since, on average, de-allocations are expected to occur in locations that may be ideal for future allocations.
However, some systems do not exhibit this behavior. Instead, this mode of operation has the effect of packing all the high temperature data into those storage locations having the fastest response times, often leaving little or no room to accommodate newly-added data. With the use of an “optimize system” VSS mode, in which substantial system resources are devoted to migrating data to optimal locations, data can be packed into most, if not all available high speed storage locations within the system in a matter of days.